Single active-layer structured dual-function devices using hybrid polymer–quantumdots

Abstract

We demonstrate hybrid polymer–quantum dot dual-function devices with a single active-layerstructure consisting of CdSe/ZnS semiconductor quantum dots dispersed with polyN-vinylcarbazole(PVK) and 1,3,5-tirs-(N-phenylbenzimidazol-2-yl) benzene (TPBi) fabricated on an indium–tin-oxide (ITO)/glasssubstrate by using a simple spin-coating technique. The dual-function devices are composedof light-emitting diodes (LED) on the top side and nonvolatile organic bistable memorydevices (OBD) on the bottom side and can show electroluminescence (EL) along withelectrical bistability concurrently. Both the functionality of LEDs and OBDs can besuccessfully achieved by adding an electron transport layer (ETL) TPBi to the OBD toattain an LED in which the lowest unoccupied molecular orbital (LUMO) level of TPBi ispositioned at the energy level between the conduction band of CdSe/ZnS and the LiF/Alelectrode. Through transmission electron microscopy (TEM) study, it is revealed thatCdSe/ZnS QDs distributed on the interface of the hole transport layer (HTL) and ETLsignificantly take part in the electroluminescence process rather than those existing at theouter surface of the ETL.